Combustion apparatus for blast furnaces

ABSTRACT

A combustion apparatus for a blast furnace for providing complete combustion beyond the tuyeres by injecting a hot blast which is caused to swirl in a blow pipe and into the furnace, causing oxygen or oxygen enriching air to swirl in a burner and into said blow pipe and adding fuels to the burner.

United States Pat e111 Shimotsuma et a1.

[451 Sept. 11,1973

Filed:

COMBUSTION APPARATUS FOR BLAST FURNACES lnventors: Teruo Shimotsuma; Kazuo Kunioka,

both of Yokohama; Takeo Yamada, Hodogayaku, Yokohama, all of Japan Nippon Kokan Kabushiki Kaisha, Tokyo, Japan Mar 26, 1971 Appl. No.: 128,377

Assignee:

US. Cl.

Int. Cl. C2lb 7/16 Field of Search 266/34 L, 41; 12216.6; 110/1825; 75/41, 42; 239/1321,

References Cited UNITED STATES PATENTS Demalander 266/41 3/1965 Smith 266/41 X 1,007,149 10/1911 Smith 1,793,849 2/1931 Groninger 266/41 1,964,727 7/1934 Fleming 75/42 X 2,454,892 11/1948 Sprow 12216.6 X 2,538,446 1/1951 Escher 122/66 2,560,074 7/1951 Bloomer... 110/1825 3,310,238 3/1967 Bryant 266/34 L Primary Examiner-J. Spencer Overholser Assistant Examiner-John S. Brown Attorriey-William C. Linton et al.

[ 5 7 ABSTRACT A combustion apparatus for a blast furnace for providing complete combustion beyond the tuyeres by injecting a hot blast which is caused to swirl in ablow pipe and into the furnace, causing oxygen or oxygen enriching air to swirl in a burner and into said blow pipe and adding fuels to the burner.

1 Claim, 5 Drawing Figures PATENTEU'SEPI 1 ms 3.758.090

sum 1 BF 2 TERUO SHIMOTSIIM MENTOR: RN 0 TAKEO YABIQDIEAGQZUO KUN/OKA ATTORNEYS PATENTEDSEPI 1 [91s 3.758.090

SHEET 2 0F 2 INVENTORS TERUO SH/MOTSUMA, A200 TAKEO mmnug K Wm'mm avg:

ATTORNEYS reducing gases such'as CO and H whichare generated at a place beyond said tuyeres from said combustion of the various fuels. In such a case, an oxygen enriched blast has also been employedalong with said injection.

As a more improved example, the Texaco Process has been published. U. S. Pat. No. 2,837,419 is an example. According to said Patent, a portion of the reducing gas required in the furnace is generated in a separate gas generator, which is, in many cases, desirable to generate all of the reducing gases in the gas generator. This reducing gas generator is operated at a temperature within the range of from about 2,000 to 3,000F and then said reducing gases are introduced into the lower part of the furnace. Thus, part or all of the coke required for conventional blast furnace operations may be eliminated. t

It will be, however, understood that many defects are recognized in either of the processes in that reducing gases are generated 'at a place beyond tuyeres or in a separate gas generator. That is, the disadvantages in the former process are as follows:

1. When the fuel injection amount is over that of the theoretical limit, the amount' of said coke comsumption tends to increase conversely.

2. In said fuel injection process through tuyeres, oxygen should be added and the hot-blast temperature be raised along with the injecting of said fuel, because the theoretical combustion temperature lowers with said fuel injection.

3. If only tuyere-injected fuels are increased without the adding of oxygen and the raising of hot-blast temperature, the substitution rate of coke lowers and then the operating conditions of said furnace will grow worse. It is needless to say that a defective combustion will be brought about. It is well-known that the required amount of injected fuels, which is possible to maintain a stable operations of said furnace, isabout SOKg/pig t in the case of heavy oil.

The disadvantages in the latter process are as follows:

I. First, a separate gas generator is necessary to generate reducing gases. It will be unavoidable that the apparatus be on a large scale and accordingly causes higher costs and requires complex operations.

2. Secondly, most refractory lining materials of said generator rapidly deteriorate at an elevated temperature. Accordingly, the temperature of said reducing gases is lower than that of said combustion zone beyond the tuyeres. It will be compelled to be injected into upper place of said tuyeres. Therefore, it is needless to say that another injecting devices should be set up separately from said tuyeres.

'3. Thirdly, when the injecting devices are set up at an upper place separately from said tuyeres, the flow of said reducing gases tends to be disproportioned and consequently a certain loss of heat will result in increase.

Thus, it is unquestionable that the efficiency of utilizing said reducing gases and said fuels will lower respectively or together. Therefore, this invention aims at the eliminating of the above-mentioned defects. The features lie in the adding of said fuels atomized with oxygen or oxygen enriching air to combustion air injected into the furnace wherein a certain rate of turning movement is given to said oxygen or oxygen enriching air and said combustion air, respectively.

An object of this invention is to provide an improved combustion process and an apparatus for a blast furnace, which is capable of displaying the best efficiency of utilizing said reducing gases and said injecting fuels.

A further object of this invention is to provide an improved combustion process and an apparatus for a blast furnace wherein the most suitable combustion temperature at a place beyond the tuyeres and complete combustion are possible to be maintained with ease and stability.

Another object of this invention is to provide an improved combustion process having agood cooling effect for the tuyeres and blowingpipes.

Other objects and advantages will be apparent from the following detailed description and with the accompanying drawings in which:

FIG. 1 is an explanatory sectional view of a structure according to this invention and its manner of operation.

FIG. 2 is an enlarged sectional view of the burner for the addition of liquid fuels.

FIG. 3 is a plan view of a modified embodiment wherein the blast structure in a blowing pipe is shown.

FIG. 4 is a side view of FIG. 3.

FIG. 5 is a sectional view taken along the line of V V in FIG. 3.

With reference to FIG. 1, the numeral 1 designates a part of the bosh of the blast furnace. The tuyere 2 is set up to said bosh l and the blow pipe 3 is inserted into said tuyere 2. This apparatus is characterized in that a swirl vane 4 is fixed to the inside of said blow pipe 3, which is capable of giving a turning movement to the hot-blast by said swirl vane 4. Into such a blow pipe 3 a burner 5 is inserted and another swirl vane 10 should also be fixed to the insideof said burner 5. This is another feature of this invention. With such a device, a turning movement is possible to be easily given to a blast of oxygen or oxygen enriching air.

The outline of such a burner 5 is shown in FIG. 2. The numeral 6 designates a burner body and the structure of said body 6 is composed of three passages. That is, around a feeding pipe of said liquid fuel 9 as a center, there is a feeding pipe of oxygen or oxygen enriching air 7,8 and next, a feeding pipe of a coolant 12,13

is formed respectively as shown in FIG. 2. The abovementioned swirl vane 10 should be fixed to the inside of said oxygen feeding pipe 8 and around said fuel feed- I ing pipe 9. When said burner is composed as mentioned above, the swirling flow of said oxygen is introduced into said blow pipe 3 along with the atomizing of said fuel. In such a case, the same swirling direction as that of the hot-blast said blow pipe is given to said oxygen flow. The delivery side of said burner should be formed, as super expansion of said oxygen swirling flow is brought about. Therefore, said delivery side is shaped as a kind of the known Laval type nozzle. At least,

with such means, a supersonic speed of said flow may be easily attained. However, the divergent portion of the nozzle employed in this invention differs from La val" type nozzle on the point at which the crosssectional area of said divergent portion flares outwardly in a step like configuration which flaring is not continuous. The position that said cross-sectional area starts to flare outwardly should be selected from a portion B which is 60 percent to 90 percent of the distance A, see FIG. 2, of the ideal divergent portion length. Such a nozzle brings about said superexpansion, makes a strong and stable backward flow form in and around the exit of said nozzle, and effectively contributes to the generating of said reducing gases and to the stabilizing of short fire flame.

Such a type of nozzle is a further feature of this invention. Thus, when the swirling flow of said oxygen or oxygen enriching air wherein said liquid fuel is atomized, is introduced into said other swirling flow of the hot blast, said atomized fuel is ignited and a strong backward flow is brought about at the place beyond said tuyeres 11 in combination with the abovementionedbackward flow blowing about in and around the exit of said burner nozzle. By such a backward flow, the reaction of said reducing-gasifying is accelerated rapidly. Thus, a feature of this invention process lies in that the swirling flow of said oxygen or oxygen enriching air wherein said fuel is atomized, is introduced into another swirling flow of said hot-blast with a supersonic speed. In such a, case, if the rate of fuel blowing amount, hot-blast amount and oxygen amount is selected accordingly, said reducing gas having the temperature equivalent to the theoretical combustion temperature at the place beyond the tuyeres can be made to generate with ease. The swirling ratio N of the above-mentioned swirling flows should be selected from the range of 0.9 to 1.5 respectively, which is given the circumference at a fixing hole of said feeding pipe.

The swirling ratio N in such a case should also be selected from the range of 0.9 to 1.5, which is given by the following formula:

N Sin a/2Az( 1141 COS a/2A2) Where A blowing cross-sectional area of blow pipe 3 A blowing cross-sectional area of feeding pipe 16 d: angle formed between the axis of feeding pipe 16 and blow pipe 3 The constituent of said reducing gas, which generates with the above-mentioned process and apparatus, is decided by the proportion of total oxygen flow amount to fuel flow amount, which changes with the constituent of said fuel as is well-known. When this invention process is applied to said reducing gas blowing process, said combustion temperature may be controlled by the oxygen enriching rate on the basis of the factors that is the fuel constituent, fuel amount per pig t, hot-blast temperature and blast humidity. On the other hand, when this invention process is applied to said fuel blowing process, the required constituent of said reducing gas may be attained by controlling the flow rate of said total oxygen amount to said fuel amount. Accordingly, even though any process as mentioned above is employed. To make the actual combustion temperature conform to said theoretical combustion temperature at the place beyond the tuyeres is possible to be carried out. The results of actual operations of conventional blast furnace is as follows:

Reducing gas Common operations Prior art Fuel blowing blowing without operations operations operations blowing oi with blowing according to according to heavy oil of heavy oil this invention this invention Increasing rate of pig iron ercent) 10.2 32. 2 38. 6 Decrease of coke rate (kg./p i g t) 60 215 Blowing fuel Blowing amount of fuel (kgJpig t) 220 280 Rate of oxygen enrichment (percent)- 37 42 Theoretical combustion temperature 0 2,100 2,100 Atmizing agent Swirling ratio of atrnizing agent. 1.3 1.3 Swirling ratio of blast 1. 3 l. 3

1 C heavy oil.

2 Pure oxygen.

by the following formula:

N UO/UZ According to the above table, it will be well understood that the effect of this invention process is far more excellent than any of the prior art. It is worthy of special mention that the effects that this invention process applied to said reducing gas flowing process is best. It is needless to say that such effects are based on that the above-mentioned defects of said reducing gas blowing process is eliminated with this invention process.

We claim:

1. In a combustion system for blast furnace, an improved combustion apparatus comprising a blow pipe for hot-blast, a swirl vane is fixed to the inside of said pipe, a burner for fuels is inserted into saidpipe, a second swirl vane is fixed to the inside of the burner passage for oxygen or oxygen enrichment air and is around a center passage of the burner for the fuels, delivery side of said burner being a divergentt'ype and'the crosssectional area of the divergent portion increases in a ously starts t a di f 60 to 90 percent of id didiscontinuously manner and the portion of said burner vergent portion length. at which the cross-sectional area increases discontinu- 

1. In a combustion system for blast furnace, an improved combustion apparatus comprising a blow pipe for hot-blast, a swirl vane is fixed to the inside of said pipe, a burner for fuels is inserted into said pipe, a second swirl vane is fixed to the inside of the burner passage for oxygen or oxygen enrichment air and is around a center passage of the burner for the fuels, delivery side of said burner being a divergent type and the cross-sectional area of the divergent portion increases in a discontinuously manner and the portion of said burner at which the cross-sectional area increases discontinuously starts at a distance of 60 to 90 percent of said divergent portion length. 